Video: Launch delayed

CAPE CANAVERAL, Fla. — NASA managers have extended their hold on the shuttle Atlantis' launch until at least Friday, to give engineers more time to study a problem with one of the ship's three onboard fuel cells, NBC News reported Wednesday.

The fueling of the external tank had yet to start when a coolant pump that chills the system used to generate electricity on Atlantis gave an erratic reading. The electrical system is made up of three fuel cells.

The space agency planned to further examine the problem, consult with the fuel cells' manufacturer and, if possible, try to launch Atlantis at 11:40 a.m. Friday. If NASA can't launch Atlantis on Friday, liftoff would have to be delayed for weeks.

Astronaut Jeff Williams, 220 miles above Earth at the space station, wasn't optimistic when Mission Control told him about the problem.

"That doesn't sound promising," he said.

Mission Control responded, "It's hard to say. We want to be ever hopeful."

NASA had planned to begin pumping 500,000 gallons of cryogenic propellants into the shuttle's tank early Wednesday in preparation for launch on a mission to resume construction of the international space station.

However, when managers met to review Atlantis' launch preparations, they learned that one of the ship's fuel cells, which combine liquid hydrogen and liquid oxygen during the flight to produce electricity, had a problem as it was powered for flight.

"The launch rules say you need to have three good, operating fuel cells," said NASA spokesman Bruce Buckingham. "We're going to see if it's something that's a real problem or whether it's something we can rectify."

Mission managers had until 4 a.m. ET to decide whether to begin filling the external fuel tank or miss Wednesday's launch window. Shortly after the appointed time, NASA announced the delay — and the managers continued to study the problem throughout the day.

NBC News quoted sources familiar with the discussions as saying that NASA would pass up a launch opportunity on Thursday while engineers continued to assess the fuel cell problem. The sources spoke on condition of anonymity because they were not authorized to make the formal announcement of an extended delay.

If a shuttle launch on Friday is ruled out, NASA would have to wait until October, when lighting and other conditions will again be suitable for a flight to the space station.

NASA originally had planned to launch Atlantis and its six-member crew last week, but a lightning strike and a storm triggered a series of postponements. The mission already has been delayed more than three years while NASA recovered from the 2003 Columbia disaster.

Focusing on fuel-tank foam
Since the accident, which claimed the lives of seven astronauts, NASA has flown two test missions to check safety improvements. The accident was traced to a piece of foam insulation that fell off shuttle Columbia's fuel tank during launch and smashed into the ship's wing, damaging its heat shield. The shuttle broke apart as it flew through the atmosphere toward landing.

Despite two redesigns of the fuel tank, managers still expect foam to fly off during launch. The debris, however, is expected to be small enough and detach late enough so that it does not pose a threat to the shuttle.

A third redesign is under way to reduce the risk of foam falling off metal brackets near the top of the tank. The modifications were not ready in time to be tested on shuttle Discovery's flight in July, but NASA approved that mission, as well as Atlantis', because even under the worst-case scenario, the crew would not be at risk.

If the shuttle is too damaged to safely return home, the astronauts would stay aboard the space station until a rescue mission could be launched. That option was not available to the Columbia crew, which was not even aware that their ship had been damaged.

NASA now requires its crews to conduct extensive in-flight inspections to assure the heat shield is safe for re-entry.

Shuttle program manager Wayne Hale said he expects the next tank modification to be made early next year.

Space station milestone
Atlantis' mission will be the first dedicated to expanding the half-built international space station since before the Columbia tragedy. Construction of the station, a multibillion-dollar, multinational effort led by the United States and Russia, began in 1998.

The space station is still operating on temporary power and cooling systems, which support a U.S. science laboratory, a connecting node, two air locks, living quarters, a fuel storage module, five pieces of structural truss and other equipment.

More than a dozen major components are awaiting rides on the shuttles, the only vehicles designed to haul them into orbit.

Atlantis' payload bay is filled with a 17.5-ton double truss segment containing a pair of solar arrays expected to double the electricity available for the station's systems and equipment.

NASA needs the additional power for laboratories built by the European Space Agency and Japan set to launch beginning next year. Before the labs are installed, NASA must finish the station's truss, and add two more sets of solar arrays in addition to the one being delivered aboard Atlantis.

"It's very difficult to compare it to moonwalks or other things we have done in the past," he added. "Clearly these are the most complicated spacewalk and assembly tasks that have ever been done before."

NASA is racing the clock with just three shuttles to finish assembling the space station before the winged spacecraft are retired in 2010. Instead of the expensive and labor-intensive shuttles, NASA wants to return to flying capsules, launched aboard expendable rockets, that can travel to the station as well as the moon and beyond.

The 12 orbiting astronauts on the International Space Station were hailed by the chief on Thursday — and also got a humorous scolding for keeping their android crewmate locked up in its packing for so long.